package com.gzsxy.JUC.rw;

import java.util.HashMap;
import java.util.Map;

import java.util.concurrent.locks.ReadWriteLock;

import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * 独占锁（写锁）  一次只能被一个线程占有
 * 共享锁（读锁）  多个线程可以同时占有
 * <p>
 * 读-读 可以共存
 * 读写 不能不存
 * 写写 不能共存
 */
public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCacheLock myCache = new MyCacheLock();

        //写入
        for (int i = 0; i < 5; i++) {
            final int temp = i;
            new Thread(() -> {
                myCache.put(temp + "", temp + "");
            }, String.valueOf(i)).start();
        }


        //读取
        for (int i = 0; i < 5; i++) {
            final int temp = i;
            new Thread(() -> {
                myCache.get(temp + "");
            }, String.valueOf(i)).start();
        }


    }
}


class MyCacheLock {

    //读写锁：更加细粒度的控制
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
//    private Lock lock = new ReentrantLock();


    private volatile Map<String, Object> map = new HashMap<>();

    //存 ，写的时候，只希望同时只有一个线程写
    public void put(String key, Object value) {

        readWriteLock.writeLock().lock();

        try {
            System.out.println(Thread.currentThread().getName() + "写入" + key);
            map.put(key, value);
            System.out.println(Thread.currentThread().getName() + "写入ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.writeLock().unlock();
        }
    }

    //取，读  所有人都可以读
    public void get(String key) {
        readWriteLock.readLock().lock();

        try {
            System.out.println(Thread.currentThread().getName() + "读取" + key);
            Object o = map.get(key);
            System.out.println(Thread.currentThread().getName() + "读取ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.readLock().unlock();
        }
    }
}


/**
 * 自定义缓存
 */

class MyCache {
    private volatile Map<String, Object> map = new HashMap<>();

    //存 ，写的时候，只希望同时只有一个线程写
    public void put(String key, Object value) {
        System.out.println(Thread.currentThread().getName() + "写入" + key);
        map.put(key, value);
        System.out.println(Thread.currentThread().getName() + "写入ok");
    }

    //取，读  所有人都可以读
    public void get(String key) {
        System.out.println(Thread.currentThread().getName() + "读取" + key);
        Object o = map.get(key);
        System.out.println(Thread.currentThread().getName() + "写入ok");
    }
}




